1. Technical Field
This invention generally relates to data processing, and more specifically relates to file systems on a logically partitioned computer system.
2. Background Art
Computer systems typically include a combination of hardware and software. The combination of hardware and software on a particular computer system defines a computing environment. Different hardware platforms and different operating systems thus provide different computing environments. In recent years, engineers have recognized that it is possible to provide different computing environments on the same physical computer system by logically partitioning the computer system resources into different computing environments. The IBM eServer iSeries computer system developed by IBM is an example of a computer system that support logical partitioning. If logical partitioning on an eServer iSeries computer system is desired, partition manager code (referred to as a “hypervisor” in IBM terminology) is installed that allows defining different computing environments on the same platform. Once the partition manager is installed, logical partitions may be created that define different computing environments. The partition manager manages the logical partitions to assure that they can share needed resources in the computer system while maintaining the separate computing environments defined by the logical partitions.
A computer system that includes multiple logical partitions typically shares resources between the logical partitions. For example, a computer system with a single CPU could have two logical partitions defined, with 50% of the CPU allocated to each logical partition, with 33% of the memory allocated to the first logical partition and 67% of the memory allocated to the second logical partition, and with two different IO slots allocated to the two logical partitions, one per partition. Once logical partitions are defined and shared resources are allocated to the logical partitions, each logical partition acts as a separate computer system. Thus, in the example above that has a single computer system with two logical partitions, the two logical partitions will appear for all practical purposes to be two separate and distinct computer systems.
Known methods for sharing information between logical partitions typically use a virtual local area network (VLAN). Using VLAN technology, logical partitions may communicate with each other on connections that appear to be physical network connections, when in reality they are virtual network connections between the logical partitions.
At times it may be desirable for logical partitions to share data. A file system is one type of data that may need to be shared, thereby allowing two different logical partitions to access the same file. Using a VLAN to share a file system would introduce significant processing overhead in the form of virtual network traffic and a software stack to support the communications protocol. Without a way to share a file system between logical partitions in a convenient and efficient manner, the computer industry will continue to suffer from inefficient manual methods for sharing data between logical partitions.